Long term preservation of organs at deep subzero temperature may allow for increased availability in donor organs. The main difficulty in achieving cryopreservation of whole organs is the difficulty in obtaining uniform freeze and thaw rates of these large masses of tissue. Utilizing programmable conduction freezing with liquid nitrogen vapor we have been able to achieve a fairly uniform rate of freeezing. In addition, using microwave thawing techniques combining 15 and 2450 MHZ we have been able to achieve thaw rates in excess of 20 to 30 degrees C/minute with little risk of thermal runaway. Although re-implantation studies to date have not been able to establish life-supporting function in any cryopreserved kidney, the ability to uniformly freeze and thaw kidneys allows for more detailed examination of freeze thaw injury in whole organs. Cannine kidneys will be perfused with various cryoprotectants and varying concentrations. The principal cryoprotectants to be used will be Dimethylsulfoxide and Ethylene glycol. At freeze rates from 1 to 5 degrees C/minute and using the previously discussed microwave thawing techniques auto-transplants of canine kidneys will be performed. Function will be determined by thhe ability of the cryopreserved organ to maintain renal function following controlateral nephrectomy. Hopefully, by refinement of various technical aspects of freezing and thawing of the organs, we will be able to improve the results following cryopreservation of whole organs.